It is common in applications, such as in insulated glass units (IGUs), to evacuate a sealed enclosed space and fill that space with an inert gas, such as argon. Knowing the conditions within the sealed enclosure are important for a number of reasons, including certification, research and development, warranty, code creation and implementation, material evaluation, and test method evaluation. Thus, conditions within the sealed enclosure must be measured.
A typical method of performing a measurement is to withdraw a sample of the gas from the enclosure and measure the sample to determine the percentage of inert gas present. However, the conventional methods for performing such measurements have notable deficiencies. For example:                1) Raman laser spectroscopy: measures oxygen only;        2) Spark Gap using differences in gap distance an electrical spark can jump: readings can be affected by glass thickness and/or metallic coatings. It also requires operator interpretation;        3) Laser or bulb frequency shift, Zeeman effect: measures oxygen only. Readings are further compromised by ambient oxygen on the outside of the sealed unit;        4) Penetrate gas sampling using oxygen analyzers or gas chromatography: oxygen analyzers, employed by themselves, can very accurately measure oxygen, but if an inert gas and oxygen mixture must be analyzed, then one would have to utilize extrapolation to calculate the fill gas only using the concentration of oxygen in the sample. The extrapolation requires the oxygen and nitrogen in the sample gas being measured to be in the same ratio as what is found in the calibration gas, typically room air (O2=20.95%, N2=78.09%). If the oxygen/nitrogen ratio in a sealed package, container or IGU becomes skewed by outside factors (desiccant adsorption, differential permeability, etc.) then oxygen analysis extrapolation becomes grossly inaccurate;        5) Metal “sensor” placed in sealed cavity that changes color in presence of oxygen: measures oxygen only;        6) Optical fluorescence: small sensor “dots” placed in cavity to measure oxygen (MOCON OpTech and others) measures oxygen only. Sensors can be affected by UV;        7) Guarded hotplates that measure the thermal energy transfer from one glass surface to another: bulky to use and slow to acquire steady-state conditions;        8) Battery powered temperature and pressure data loggers: batteries may die or leak;        9) Spark Emission Spectroscopy (SES) analyses of the light spectra from a high voltage spark inside a sealed insulating glass cavity: these have manufacturer stated inaccuracies as high as ±5% at concentration levels below 85%. Readings are dependent on oxygen and nitrogen to be in the same ratio as that found in ambient air;        10) Gas chromatographs (GC): can be cumbersome to use and extracting a quality sample from an IGU using a syringe is difficult and requires a skilled operator to perform. This type of gas sampling is prone to introduce contamination into the test sample which will result in low reliability, repeatability, and accuracy. This type of testing also compromises the seal integrity of the package, container, or IGU; and        11) Thermal conductivity sensors arranged in a Wheatstone bridge: requires precisely matched resistive filaments and offset resistors. Wheatstone bridge circuits require one out of the two resistive filaments to be in a stream of reference gas. Thus, measuring the thermal conductivity of a gas in a sealed container is not possible using a Wheatstone bridge configuration.        
Moreover, invasive measurement techniques compromise the integrity of the enclosure. Withdrawing a sample from an enclosure is not only difficult to do, but the potential for error and contamination of the sample is probable since the sample is transferred from the sealed cavity to the analysis instrument.
In addition, many types of sensors are inherently bulky and/or require wired power and communication lines that prevent the enclosure from being formed with internal sensor packages.
Thus, there is a need for improved devices, systems and methods to measure the conditions within a sealed enclosure.